1. Field of the Invention
The present invention relates to development devices, particularly to a development device that forms a toner image using a developer including toner and carrier.
2. Description of Related Art
As a conventionally general development device, for example, a development device described in Japanese Patent Laid-Open Publication No. 2011-2760 is known. FIG. 7 is a cross-sectional view of the development device 500 described in Japanese Patent Laid-Open Publication No. 2011-2760. FIG. 8 is a top view of the development device 500 described in Japanese Patent Laid-Open Publication No. 2011-2760. In the following, the vertical direction is defined as a z-axis direction, the longitudinal direction of the development device 500 as an x-axis direction, and a direction perpendicular to the x-axis direction and the z-axis direction as a y-axis direction.
The development device 500 includes a housing 502, stirring screws 504 and 506, a conveying screw 508, and a developing roller 510. The housing 502 has formed therein a developer stirring portion Sp11, a developer supply and recovery portion Sp12, and communicating portions R11 and R12. The developer stirring portion Sp11 and the developer supply and recovery portion Sp12 communicates with each other at both ends via the communicating portions R11 and R12.
The stirring screws 504 and 506 extend in the x-axis direction within the developer stirring portion Sp11, and convey a developer in the positive x-axis direction. The developer conveyed by the stirring screws 504 and 506 flows into the developer supply and recovery portion Sp12 via the communicating portion R11.
The conveying screw 508 extends in the x-axis direction within the developer supply and recovery portion Sp12, and conveys the developer in the negative x-axis direction. The developer conveyed by the conveying screw 508 flows into the developer stirring portion Sp11 via the communicating portion R12.
The developing roller 510 is provided in the developer supply and recovery portion Sp12, and supports the developer being conveyed by the conveying screw 508, on the periphery.
In the development device 500 thus configured, the developer is sequentially conveyed and circulated through the developer stirring portion Sp11, the communicating portion R11, the developer supply and recovery portion Sp12, and the communicating portion R12, in the same order.
Incidentally, the development device 500 might have uneven density in a toner image. More specifically, there might be an insufficient amount of developer flowing from the communicating portion R11 into the developer supply and recovery portion Sp12. In such a case, a sufficient amount of developer can be supported in the vicinity of an end of the developing roller 510 on the positive x-axis direction side but cannot be supported in the vicinity of an end of the developing roller 510 on the negative x-axis direction side. As a result, uneven density might occur in a toner image developed on a photoreceptor by the developing roller 510.